J Korean Med Sci 2006; 21: 247-52 ISSN 1011-8934
Copyright � The Korean Academy of Medical Sciences
Association Between Sensitization to Outdoor Spider Mites and Clinical Manifestations of Asthma and Rhinitis in the General Population of Adults It has been demonstrated that spider mites such as the two-spotted spider mite (Tetranychus urticae) are important allergens for fruit farmers. A total of 2,467 adults (795 metropolitan urban, 788 non-metropolitan urban, and 884 rural subjects) were enrolled. They responded to the questionnaire, and underwent methacholine bronchial provocation tests as well as skin prick tests to locally common aeroallergens including the two-spotted spider mite. The prevalences of asthma and rhinitis as reported on the questionnaire were 7.8% and 16.4% of adults aged 20-35, 9.4% and 24.7% of those 36-50, and 17.7% and 21.7% of those older than 50, respectively. Among the older group, the two-spotted spider mite was the most common sensitizing allergen, although it was second of that of house dust mites among the other two age groups. Sensitization to the two-spotted spider mite was significantly associated with the prevalence of asthma and rhinitis among the younger age group, and associated with the prevalence of rhinitis among the older age group. The twospotted spider mite might be a common sensitizing allergen in the general population of adults, and sensitization to this mite may play a role in the manifestation of asthma and rhinitis symptoms during adulthood.
Tae-Bum Kim*,�, Yoon-Keun Kim*,�, Yoon-Seok Chang*,�, Sang-Hoon Kim*,�, Sung-Chul Hong�, Young-Koo Jee�, Sang-Heon Cho*,�, Kyung-Up Min*,�, You-Young Kim*,� Department of Internal Medicine*, Seoul National University College of Medicine; Institute of Allergy and � Clinical Immunology , Seoul National University Medical Research Center, Seoul; Department of Preventive � Medicine , Cheju National University College of � Medicine, Cheju; Department of Internal Medicine , Dangook University College of Medicine, Cheonan, Korea Received : 14 March 2005 Accepted : 5 October 2005
Address for correspondence You-Young Kim, M.D. Department of Internal Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea Tel : +82.2-2072-2232, Fax : +82.2-762-9662 E-mail :
[email protected] *This study was supported by a grant from the Korea Health 21 R & D Project, Korean Ministry of Health & Welfare (Grant No., 03-PJ10-PG13-GD01-0002) and Seoul National University Hospital (Grant No., 03-2000012-0).
Key Words : Tetranychidae; Spider Mites; Asthma; Rhinitis
INTRODUCTION
tant indoor allergens in Korean children (4). Meanwhile, it is the spider mites (family Tetranychidae), forming the family of phytophagous mites, which have the heavist economic burden on agriculture. All spider mites are outdoor phytophagous mites causing significant damage to fruit leaves throughout the world, and belong to the suborder Prostigmata of the order Acari, while house dust mites belong to the suborder Astigmata of the same order. Although predaceous mites do indeed attack spider mites, the predator complex currently in place does not usually control spider mites, particularly when organic phosphates or sulfur spray programs upset natural control (5). Although spider mites were negligible pests in fruit-cultivation before World War II, their number has increased in the fruit-cultivation industry since pesticides were introduced to eliminate fruit moths 40 yr ago. Surveys have demonstrated that the two-spotted spider
Asthma is a worldwide problem considered to be more common in developed countries than in developing countries. Although asthma is a common cause of morbidity in adults, the perception remains that it is a childhood disease. Asthma incidence is higher in children than in adults, and remissions are unlikely after the age of 30 yr (1, 2). In children, there is an association between the presence of atopy and the prevalence of asthma and rhinitis during childhood (3). However, there have been relatively few population studies of asthma prevalence and association between atopy and asthma during adulthood. Asthma and allergic rhinitis due to indoor house dust are major health problem worldwide, and house dust mites Dermatophagoides farinae and D. pteronyssinus are the most impor247
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mite (Tetranychus urticae, TSM) is one of the most common pests in herbaceous plants and fruit leaves. Our previous cross-sectional studies demonstrated that spider mites are important allergens in the development of work-related asthma and rhinitis in fruit farmers (6, 7). The aim of our present study was to evaluate the association between sensitization to TSM and clinical manifestations of asthma and rhinitis in the general population of adults living in urban and rural areas.
MATERIALS AND METHODS Populations
A total of 2,467 adults over 20 yr, 795 of whom were living in metropolitan city (Seoul), 788 in non-metropolitan cities (Cheonan and Icheon), and 884 in rural area (Khoisan), were randomly enrolled in this study. The male female ratio was the same in all three groups. The questionnaire response rate was 2,432 subjects, with 2,401 undergoing skin prick tests to locally common aeroallergens including the TSM and 1,858 methacholine bronchial provocation tests. All the subjects gave informed written consent and the study protocol was approved by the Ethics Committee of Seoul National University Hospital. Methods
A modified questionnaire developed by the International Study of Asthma and Allergic diseases in Children (ISAAC) (8) was translated into Korean, of which validity was already studied (9, 10), with demographic data, asthma and rhinitis symptoms, and various risk factors, such as family history of asthma and allergic rhinitis and active cigarette smoking being included. The symptoms of asthma were wheezing, breathlessness, and recurrent nocturnal cough during the previous 12 months, and asthma was regarded as having been positively tested if a subject had experienced two or more of these asthma symptoms. Rhinitis symptoms were sneezing, and runny or blocked nose with itchy eyes during the previous 12 months when a subject did not have a cold or the ‘flu’. Skin prick tests were performed using a panel of 12 common Korean aeroallergens. None of the subjects had received antihistamines orally for five days preceding the tests. The panel consisted of house dust mites (Dermatophagoides pteronyssinus, D. farinae), cat fur, molds (Aspergillus fumigatus, Alternaria tenuis), various pollens (tree pollen mixture 1 [alder, hazel, popular, elm, and willow tree] & 2 [birch, beech, oak, and plane tree], grass pollen mixture [velvet grass, orchard grass, rye grass, timothy grass, Kentucky blue grass, and meadow grass], mugwort, and ragweed), German cockroach (Blattella germanica), and TSM (0.1 mg/mL). TSM was obtained from
both the Apple Research Institute, Kyungbuk, Korea, and were extracted as previously described (7). A positive control of histamine (1 mg/mL) along with a negative diluent control was included in all tests. Fifteen minutes after the prick, the mean diameter of the wheal formed by the allergen was compared with that formed by histamine. If the former was greater or equal to the latter (allergen/histamine ratio ≥1.0), the reaction was defined as positive. Atopy was defined if a subject exhibited positive skin-test responses to any one or more of the 12 aeroallergens. Forced expiratory volume in 1 sec (FEV1) and forced vital capacity (FVC) were measured with a portable spirometer (Micro Spirometer, Micro Medical, Rochester, Kent, U.K.), with the largest values of triplicate FEV1 and FVC measurements being adopted. Methacholine challenge was carried out to determine bronchial responsiveness using the method described by Chai et al. (11). Subjects with respiratory tract infections during the two weeks immediately prior were excluded to avoid false positive result, and those with baseline FEV1 lower than either 1,200 mL or 50% of the predictive value were also excluded to avoid the recording of severe bronchoconstrictive reaction. None of the subjects had received any bronchodilators or anti-histamines for five days preceding the challenge. Concentrations of 2.5, 6.25, 12.5, and 25 mg/mL of methacholine were prepared by dilution with buffered saline. A Rosenthal-French dosimeter (Laboratory for Applied Immunology, Baltimore, MD., U.S.A.) was used to deliver the aerosol generated by a nebulizer (DeVilbiss, Somerset, PA, U.S.A.). Subjects inhaled five inspiratory capacity breaths of increasing methacholine concentration until either FEV1 fell to less than 80% of its baseline value or until the highest concentration was reached. The largest value of triplicate FEV1 measurements at 90 or 180 sec after each inhalation was adopted for analysis. If the concentration of methacholine which caused a 20% fall in FEV1 (PC20) was less than 25 mg/mL, the subject was considered to have airway hyperresponsiveness (AHR) to methacholine. Statistical analysis
Statistical significances of association between the clinical symptoms of asthma and rhinitis and risk factors, including sensitization to TSM were assessed using the 2 and 2-trend test. A p value of 0.05 or less was regarded as significant.
RESULTS Table 1 shows demographic and clinical characteristics of the general population according to age. The frequency of active cigarette smoking did not vary with age, but was markedly higher among men than among women. Whereas the prevalences of atopy (positive skin test responses to one or more common allergens) and of rhinitis on the question-
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Table 1. Demographic and clinical characteristics of study populations according to age group
Table 2. Relationship between the prevalence of clinical asthma by questionnaire and risk factors according to age
Age (yr) ≤35 (n=709) Sex, female (%) 346 (48.8) Geographic areas Metropolitan area 288 Non-metropolitan area 257 Rural area 164 Smoking (n=2,394) 276 (39.3) Women (n=1,140) 17 (5.0) Men (n=1,254) 259 (71.9) � 162 (24.0) Family history (n=2,323) Atopy�(n= 2,467) 251 (35.4) D. pteronyssinus 107 (15.5) D. farinae 101 (14.7) T. urticae 62 (9.0) T. putrescentiae 49 (7.1) German cockroach 41 (6.0) AHR� (n=1,858) 26 (5.7) Asthma (n=2,452) 55 (7.8) Rhinitis (n=2,451) 115 (16.4) �
Clinical asthma p*
36-50 (n=934)
≥51 (n=824)
442 (47.3)
432 (48.7)
317 339 278 375 (41.4) 12 (2.9) 363 (74.7) 237 (26.7)
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